the territory scarred by the battles of the civil rights era. >> a klan bomb ripped apart birmingham's 16th street baptist church, killing four children attending bible class. >> reporter: so, we're in birmingham, alabama. and just down here is the jail where martin luther king jr. wrote the famous letter from a birmingham jail. along the way, we make a stop at the southern poverty law center, where mark potok and his colleagues have been fighting the kkk in courtrooms and classrooms for decades. many of the klanspeople we've talked to say barack obama has been our single most effective recruiting tool in the last four, five years. >> well, i think there's some truth to that. immediately after obama was elected, we saw two of the largest hate websites in the country crash. >> reporter: potok told us that by the late '80s, the klan dwindled to a few hundred. they now number closer to 6,000. >> white power! >> reporter: he believes they can be very dangerous. >> it's dangerous, not so much because a whole bunch of klansmen get together in a room and plan to murder 1,000 people with a bom